Bonding wire inductor

ABSTRACT

A vertical bonding wire inductor having a high quality (Q) factor and tunability, which can be manufactured using an existing wire bonding technology which is widely used for packaging integrated circuits, without an additional mask manufacturing process. The vertical bonding wire inductor includes at least one pair of bonding pads ( 3 ) occupying a predetermined area on a substrate ( 9 ) and one or more bonding wires ( 1 ) for connecting one or more pairs of bonding pads ( 3 ). The bonding wire ( 1 ) has a loop shape having a predetermined height. Due to the improved electrical characteristics, stability in process, tunability without an additional mask manufacturing process, and relatively low manufacturing cost, the vertical bonding wire inductor can be useful in production of economical microwaves devices.

TECHNICAL FIELD

The present invention relates to inductors, and more particularly, to aninductor used in integrated, circuits (ICs).

BACKGROUND ART

As the importance of communications services increases in modeminformation societies, high-speed, high-performance, highensity,high-reliability and low-cost electric devices are also required for ahigh quality, wide bandwidth, high data rate communication service, inaddition to increasing the capability and speed of a channel. Thus,improving the structure and performance of radio frequency ICs (RFICs)and microwave monolithic ICs (MMICs) and hybrid ICs becomes the centerof interest in the related art. In particular, improvement in theperformance of an inductor which is a basic element used in designingvoltage-controlled oscillators (VCOs), low noise amplifiers (INAs),narrow-ban impedance matching networks, high-performance linear filters,single-chip transceivers, multi-chip modules (MCMs) and low voltage/lowpower devices, which are key technologies in wireless communications, isvery important. The performance of an inductor used for such RFICs andMMICs is evaluated according to Q-factor, inductance and self-resonantfrequency, and typically an inductor having a high Q-factor is requiredin the technical field relating to the present invention [Seung-won Packand Kwang-seok Seo, 1997, Air-Gap Stacked Spiral Inductor, IEEEMicrowave and Guided Wave Letters, Vol. 7, No. 10, pp. 329-331].

Until now, horizontal spiral inductors have been used in RFICs andMMICs. However, the horizontal spiral inductor has disadvantages in thata relatively large area is occupied by the inductor with respect to theentire area of the RFIC or MMIC, and its Q-factor is low due toinevitable ohmic loss and dielectric loss. Also, due to an air-bridgeprocess for connecting the center of the spiral inductor to a port, anadditional photolithography and metallization processes are required inmanufacturing the spiral inductor. Because of these problems, it isdifficult to manufacture such a conventional spiral inductor. Also,after the manufacture of a mask used for the manufacture of the spiralinductor is completed, the inductance of an inductor manufacturedthereby is fixed. Thus, in order to obtain different inductances, aseparate mask must be manufactured for each conductor, thus increasingthe manufacturing cost.

To solve the above problems, S. Chaki et al. suggests a method forincreasing the Q-factor of an inductor by lowering resistance byincreasing the thickness or width of a stripline formed by gold (Au)[S.Chaki, S. Aono, N. Andoh, Y. Sasaki, N. Tanini and O. Ishihara, 1995,Experimental Study on Spiral Induaors, IEEE MTTs Digest, pp. 735-756; M.Hirano, Y. Imai and K. Asai, 1991, ¼ Miniaturized Passive Elements forGaAs MMICs, Proc. Of IEEE GaAs IC Symposium]. However, increasing thethickness of the stripline inevitably increases the unit cost ofproduction, makes air-bridge processing for connecting the center of theinductor to a port difficult, increases the area occupied by theinductor in the RFIC or MMIC, and thus it is not suitable for low-costmass production.

I. Woff and H. Kapusta disclose another method for solving the aboveproblems by increasing inductance by increasing the length of astripline. According to this method, however, the width of the striplineof a spiral inductor and the interval between the striplines becomenarrow, so that the resistance of the stripline increases and theQ-factor decreases. Thus, in order to increase inductance without adecrease in Q-factor, the area occupied by the spiral inductor mustincrease, thus increasing the manufacturing cost. Also, due to the lossof capacitance between a ground plane and the stripline and dielectricloss in a substrate, self-resonant frequency is liable to decrease [I.Wolf and H. Kapusta, 1987, Modeling of Circular Spiral Inductors forMMJCs, IEEE MITs Digest, pp. 123-126].

Also, Y. Seo et al. suggests using a multi-layered inductor as anothermethod for increasing inductance [Y. Seo and V. Tripathi, 1995, SpiralInductor in RFIC's and MMICS, Proc. of Asia Pacific MicrowaveConference, pp. 454-457; L. Zu and Y. Lu et al., 1996, High Q-factorInductors Integrated on MCM Si Substrates, IEEE Trans. on Components,Packaging, and Manufacturing Tech. Part B, Vol. 19, No. 3, pp. 635-642].Also, Y. Sun et al. reports an air-bridge inductor in which a wire issuspended from a dielectric substrate, as a method for decreasingconductance due to the capacitance and dielectric loss [Y. Sun, H. V.Zeiji, J. L. Tauritz and R. G. f. Baets, 1996, Suspended MembraneInductors and Capacitors for Application in Silicon MMIC's, IEEEMicrowave and Millimeter-Wave Monolithic Circuits Symposium Digest, pp.99-102; C. Y. Chii and G. M. Rebeiz, 1995, Planar Microwave andMillmeer-Wave Lumped Elements and Coupled-Line Filters UsingMicro-Machining Techniques, IEEE Trans. on Microwave Theory and Tech.,Vol. 43, No. 4, pp. 730-738]. However, these methods require a greatexpense for production, thus practical use thereof is difficult.

DISCLOSURE OF THE INVENTION

An object of the present invention is to improve the performance andeconomical problems of a conventional spiral inductor, and inparticular, to improve a low quality (Q) factor and a low self-resonantfrequency of the spiral inductor and difficulty in manufacturing theinductor;

Another object of the present invention is to provide a bonding wireinductor using a wire bonding technology which is widely used forintegrated circuit packaging.

Another object of the present invention is to provide an on-chipsolenoidal bonding wire inductor fabricated by a semiconductormanufacturing process.

Another object of the present invention is to provide a coupler ortransformer using two bonding wire inductors arranged adjacent to eachother.

Another object, of the present invention is to provide a surfacemounted-type bonding wire inductor for a hybrid integrated circuits.

Another object of the present invention is to provide a vertical bondingwire inductor having, high Q-factor, high self-resonant frequency, andtunability which does not need an additional mask manufacturing process.

To achieve the above objects of the present invention, there areprovided a bonding wire inductor having at least one pair of bondingpads which face each other, occupying a predetermined area on asubstrate, wherein the facing bonding pads are connected by a bondingwire which is suspended from the substrate, thus forming a loop.

A pair of bonding pads and one bonding wire form a single loop bondingwire inductor. However, a bonding, wire inductor having 2, 3 or moreloops can be manufactured as desired, and such a multiple bonding wireinductor falls within the scope of the present invention. In the case ofa multi-loop bonding wire inductor, multiple bonding wires are arrangedat a predetermined interval according to a pad pitch. As the pad pitchbecomes narrow, the structure of the inductor becomes similar to that ofa coil, increasing inductance. In the case of including two or morepairs of bonding pads, such bonding pads are arranged in two rows on asubstrate. Also, a parallel connection between each of the bonding padsof one of the two rows and the bonding pad of the other row, the padsfacing each other, and a diagonal connection between each of the bondingpads of one row and the corresponding bonding pad adjacent to the facingbonding pad of the other row, can be both connected by bonding wires asmentioned above, or the parallel or diagonal connection can be made by ametal strip which is in contact with the substrate.

Also, the bonding wire and bonding pads are ball-wedge bonded byautomatic fine pitch ball bonding. Alternatively, the connection betweenthe bonding wire and the bonding pads can be achieved by wedge-wedgebonding. In the case where the bonding wire is connected to the bondingpads by wedge-wedge bonding, the height of the loop formed by thebonding wire is lower than that in the case of using ball-wedge bonding.Also, the bonding wire and the bonding pads may be bonded by stitchbonding or ribbon bonding. In stitch bonding, the bonding length isshort and the height of the loop formed by the bonding wire is low,compared to ball bonding (ball-wedge bonding), and thus stitch bondinghas been widely used for packaging radio frequency circuits. Inparticular, the electrical performance of the bonding wire inductoraccording to the present invention is lowered by the resistance of themetal strip. Thus, by replacing the metal strip with a bonding wire,resistance of the metal strip can be decreased and unavoidablegeneration of the parasitic capacitance can be further decreased, thusincreasing the Q-factor and resonant frequency.

In addition, the bonding wire may have a ribbon or round shape, or mayhave a rectangular section. The bonding wire may be formed of gold (Au),aluminum (Al), copper (Cu) or alloys thereof, and preferably, Au isused.

The metal strip which is in contact with the substrate may be formed ofAu, Al, Cu or alloys thereof, and preferably, Au or alloys thereof isused.

According to the present invention, there is provided a method formanufacturing the bonding wire inductor, comprising the steps of formingat least one pair of bonding pads facing each other, on a substrate.Then, the facing bonding pads are connected with a bonding wire which issuspended from the substrate, thus forming a loop.

In a multi-loop bonding wire inductor having two or more pairs ofbonding pads, such as the one mentioned above, some bonding pads can beconnected by a metal strip, wherein the metal strip and the bonding padscan be formed by a lift-off method.

After a bonding process for connecting the bonding pads with bondingwires, the bonding wire inductor can be packaged with epoxy resin or canbe fixed by hermetic packaging.

A semiconductor substrate on which the bonding wire inductor accordingto the present invention can be formed, may be a gallium arsenide (GaAs)substrate, a silicon substrate, an alumina substrate, a fluorine-resinsubstrate, an epoxy substrate, a ceramic substrate, asilicon-on-insulator (SOI) substrate, a lithium tantalate (LiTaO₃)substrate, a lithium niobate (LiNbO₃ substrate, a low temperatureco-fired ceramic (LTCC) substrate, a quartz substrate, a glass substrateor a printed circuit board. Preferably, the silicon substrate or GaAssubstrate is used. In general, in the case of using a silicon substrate,an insulating layer is formed on the silicon layer, and silicon oxide(SiO₂), silicon nitride (Si₃N₄) or polyimide is used as an insulatingmaterial.

A bonding wire inductor can be achieved by fine pitch wire bondingequipment, which bonds highly elastic bonding wires having a diameter of25-100 μm. By using existing wire bonding technology used for RFICs andMMICs, which is automated and commercially available, the wire bondingcan be implemented using bonding wires having a diameter of 25 μm at aminimum pad pitch of 55 μm.

Also, the thickness of the substrate may be approximately 100-625 μm,and is preferably, about 100 μm. The line width of the metal strip maybe in the range of about 15-30 μm, and the thickness thereof may be inthe range of about 2-5 μm. The Q-factor improves as the thickness of themetal strip increases. However, increasing the thickness of the metalstrip requires additional expensive material, thereby increasing theunit cost for production. Preferably, the area of the bonding pad is inthe range of about 50×50 μm-90×90 μm. In general, the performance of adevice is improved with a decrease in the pad area, and thus the padarea can be reduced if required. The electrical characteristics of abonding wire which forms a loop having a predetermined height, byconnecting a pair of bonding pads, are improved as the diameter of thebonding wire increases. However, a bonding wire diameter of about 25 μmis desirable. Also, preferably, in ball-wedge bonding, the height of theloop is in the range of about 70-1,000 μm, and more preferably, about350 μm. Also, the bonding length between the bonding pad may be about0.5 mm.

The area occupied by the bonding wire inductor according to the presentinvention is equal to that occupied by a spiral inductor. However,because bonding wires are suspended from a substrate, the effect of themagnetic field on other devices can be minimized, in addition toreducing the substrate loss (dielectric loss). As a result, a solenoidtype inductor can be achieved, which is an ideal inductor suitable forhigh efficiency inductance. In a conventional spiral inductor, loss in asemiconductor substrate was a significant consideration in designing.Thus, in the aspect of substrate loss, the bonding wire inductoraccording to the present invention, which is suspended from thesubstrate, is highly effective in solving the problem of loss in siliconsubstrates.

Also, the bonding wire inductor according to the present invention canbe applied in a coupler or transformer, by arranging two bonding wireinductors such that they are adjacent to each other. In arranging aplurality of bonding wire inductors in a voltage controlled oscillator(VCO) or other radio frequency devices, the bonding wire inductors canbe arranged such that the directions of the magnetic fields areperpendicular to each other, in order to minimize magnetic interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example of a bonding wire inductor ona gallium arsenide (GaAs) substrate according to the present invention;

FIG. 2 is an equivalent circuit diagram illustrating the characteristicsof a bonding wire inductor according to the present invention;

FIG. 3 is a vertical sectional view of an undercut of a photoresistlayer;

FIG. 4A shows a 4-loop vertical bonding wire inductor fabricated by amethod according to the present invention; FIG. 4AA shows a side view ofthe bonding wire inductor in FIG. 4A;

FIG. 4B shows a 3.5 turn spiral inductor as a comparative example to thepresent invention;

FIG. 5 shows an example of hermetic packaging of the bonding wireinductor according to the present invention;

FIG. 6 is a graph in which the inductances of single loop bonding wireinductors having various bond-pad spacings on a GaAs substrate areplotted with respect to frequency;

FIG. 7 is a graph plotting the Q-factors of single loop bonding wireinductors having various bond-pad spacings on a GaAs substrate areplotted with respect to frequency;

FIG. 8 is a Smith chart in which the S-parameters of a 4-loop verticalbonding wire inductor (0.82 μm-thick metal strip) and a 3.5-turn spiralinductor on GaAs substrate are measured by on-wafer measurement andplotted.

FIG. 9 is a graph of the inductances of vertical bonding wire inductorsand spiral inductors, calculated using the S-parameters of FIG. 8;

FIG. 10 is a graph of the Q-factors of vertical bonding wire inductorsand spiral inductors, calculated using the S-parameters of FIG. 8;

FIG. 11 is a graph of the resistances of vertical bonding wire inductors(0.82 μm-thick metal strip) and spiral inductors on a GaAs substrate;

FIG. 12 is a graph of the inductances of vertical bonding wire inductors(2 μm-thick metal strip) and spiral inductors on a GaAs substrate;

FIG. 13 is a graph of the Q-factors of vertical bonding wire inductors(2 μm-thick metal strip) and spiral inductors on a GaAs substrate;

FIG. 14 is a graph of the inductances and the Q-factors of verticalbonding wire inductors on a GaAs substrate (2 μm-thick metal strip)before and after molding;

FIG. 15 is a graph of the inductances and the Q-factors of spiralinductors on a GaAs substrate before and after molding;

FIG. 16 is a graph of the inductances of vertical bonding wire inductorsand spiral inductors on a p-type silicon substrate (15 Ω-cm);

FIG. 17 is a graph of the Q-factors of vertical bonding wire inductorsand spiral inductors on a p-type silicon substrate (150 Ω-cm);

FIG. 18 is a graph of the inductances and the Q-factors of verticalbonding wires on a p-type silicon substrate (15 Ω-cm) before and aftermolding;

FIG. 19 is a graph of the inductances and the Q-factors of spiralinductors on a p-type silicon substrate (15 Ω-cm) before and aftermolding;

FIG. 20 is a graph of the inductances of vertical bonding wire inductorsand spiral inductors on a p-type silicon substrate (30 Ω-cm);

FIG. 21 is a graph of the Q-factors of vertical bonding wire inductorsand spiral inductors on a p-type silicon substrate (30 Ω-cm);

FIG. 22 is a graph of the inductances and the Q-factors of verticalbonding wire inductors on a p-type silicon substrate (30 Ω-cm) beforeand after molding;

FIG. 23 is a graph of the inductances and the Q-factors of spiralinductors on a p-type silicon substrate (30 Ω-cm) before and aftermolding;

FIG. 24A is a conceptual perspective view of another vertical bondingwire inductor on a GaAs substrate or silicon substrate;

FIG. 24B shows a 4-loop vertical bonding wire inductor fabricated byanother method according to the present invention;

FIGS. 24C and 24D shows another vertical bonding wire inductor on asilicon substrate (15 Ω-cm);

FIG. 25A is a graph of the Q-factors of the vertical bonding wireinductors of FIG. 24A;

FIG. 25B is a graph of the inductances of the vertical bonding wireinductors of FIG. 24C and spiral inductors;

FIG. 25C is a graph of the Q-factors of the vertical bonding wireinductor of FIG. 24C and the spiral inductors; and

FIGS. 26 and 27 shows examples of arrangement in which two bonding wireinductors according to the present invention are arranged being adjacentto, each other.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, the structure of a bonding wire inductor accordingto the present invention includes three pairs of bonding pads 3 each of70×70 μm, and metal strips 5 having a thickness of 2 μm and a line widthof 20 μm, which diagonally connect the bonding pads 3 and three bondingwires 1 each having a diameter of 25 μm, for connecting each pair ofbonding pads facing each other, which are formed on a gallium arsenate(GaAs) substrate 9 deposited to a thickness of 100 μm on a dielectric ormetallic bottom plate 11. The bonding wire 1 has a loop shape having aheight of 350 μm and the plane formed by the loop is perpendicular tothe surface of the substrate. The pad pitch which determines the wirespacing, is 80 μm and the area occupied by the bonding wire inductor is540×230 μm. Each pair of bonding pads 3 and a bonding wire 1 areball-wedge bonded each other to form a 3-loop bonding wire inductor. Thebonding wire 1 and the metal strip 5 are formed of gold (Au) and thebonding wire inductor is packaged by molding it with epoxy resin 13after the wire bonding process.

The equivalent circuit of FIG. 2 is for comparing the effectiveinductance, the Q-factor and the self-resonant frequency of the verticalbonding wire inductor according to the present invention and those of aconventional horizontal spiral inductor. In the case of the horizontalspiral inductor, C₁ and C₂ represent the self-capacitances of striplineson a semiconductor substrate, Cc represents the mutual capacitancebetween striplines, and R and L represent the resistance and inductanceof the stripline, respectively. In the case of the vertical bonding wireinductor according to the present invention, C₁ and C₂ represent thecapacitances of the stripline and bonding pad, respectively, Ccrepresents the mutual capacitance between the bonding wire and thestripline, R represents the resistance due to the substrate and ohmiclosses of the stripline and the ohmic and radiation losses of thebonding wire, and L represents the inductance of the stripline and thebonding wire.

Prior to manufacturing a vertical bonding wire inductor according to thepresent invention, the inventors simulated the wide band characteristicsof both the vertical bonding wire inductor according to the presentinvention and a conventional spiral inductor. In order to analyze thewide band characteristics, a commercially available high frequencystructure simulator (HFSS, HP85180A, manufactured by Hewlett-PackardCo.) adopting a finite element method (FEM) was used. According to thesimulation using the FEM, a 3-dimensional finite mesh was repetitivelygenerated such that the result was within a 3% error range of theconvergence region. In order to produce accurate results, a metalstripline of 50 Ω was extended such that irregular electric and magneticfields due to the electric field applied to an input port did not changethe characteristics of the inductor, and then the extended line wasde-embedded to analyze the characteristics of the inductor on thereference plane of FIG. 1. In order to take into account minor radiationeffects at the boundary of the bonding wire except for the input andoutput ports 7, a boundary condition which was the closest to the actualsituation was set by applying absorbing boundary conditions (ABC) to aposition being far away from the inductor.

A wideband simulation of the vertical bonding wire inductor, of up to 10GHz, showed improvements in inductance by approximately 6%, inself-resonant frequency by approximately 8.5% and in Q-factor byapproximately 360%, compared to those of the horizontal spiral inductorhaving the same area under the same environment.

Embodiment 1

Fabrication of Vertical Bonding Wire Inductor on GaAs Substrate

In order to effectively observe the electrical characteristics of aninductor, design parameters such as loop pitch, number of loops, linewidth, bonding pad area and bonding length were varied. The bonding padwas designed with three different sizes of 90×90 μm, 80×80 μm and 70×70μm, and pad pitches were varied to 105 μm, 100 μm and 85 μm in order toobserve the magnetic flux linkage of the inductor.

In order to fabricate the inductors according to the above design, abottom plate 11 was formed of metal or dielectric substance, and a GaAssubstrate 9 was formed thereon to a thickness of 500 μm. Four pairs ofbonding pad 3 arranged on the substrate 9 in two rows and a metalstripline 5 for diagonally connecting the bonding pads A were formed bya lift-off process.

In order to form a photoresist film suitable for the lift-off process,AZ5214 photoresist film was used, and the photoresist film was undercutby a phase transition process as shown in FIG. 3 in order to clean andeasily form a metal pattern. Chromium (Cr) was deposited to a thicknessof 200 Å on the photoresist film pattern 15 formed as shown in FIG. 3,in order to improve adhesion with the substrate 9, and Au was depositedthereon to a thickness of 0.8 μm. After the lift-off process wascompleted, the thickness and line width were measured, which were equalto the design values. A wire bonding process for connecting the bondingpads formed on the 500 μm-thick GaAs substrate was performed using aShinkawa UTC-3000 BI bonder, an automatic bonding machines used in ageneral production line, which can control the height and shape of thebonding.

The fabricated vertical bonding wire inductor according to the presentinvention is shown in FIG. 4A. The bonding wire inductor of FIG. 4A wasformed by four bonding wires having a 25 μm-diameter and a 350 μmheight, and a stripline having a 0.82 μm thickness and a 30 μm width.The bonding pad had a size of 70×70 μm and a pad pitch of 85 μm.

Thus, as shown in FIGS. 4A-4AA, a bonding wire inductor of the presentinvention may comprise a first inductor terminal (120) and a secondinductor terminal (122) formed on a substrate having a main surface; afirst bonding pad (130) connected to the first inductor terminal; asecond bonding pad (132) connected to the second inductor terminal; afirst bonding wire (100 a) connected between the first and secondbonding pads; said first bonding wire including a first member (151)bonded to the first bonding pad, a second member (153) coupled to thefirst member and rising from the main surface of the substrate in adirection opposing to the second bonding pad; a third member (155)coupled to the second member and rising up to a wire loop height in adirection toward the second bonding pad, and a fourth member (157)coupled to the third member and descending toward the second bonding padto be bonded to the second bonding pad; and said wire loop heightranging from 100 μm to 1,000 μm.

In another embodiment, as shown in FIG. 24B, a bonding wire inductor ofthe present invention may comprise a first inductor terminal (320) and asecond inductor terminal (322) formed on a substrate having a mainsurface; first bonding pad (330) connected to the first inductorterminal; second bonding pad (336) connected to the second inductorterminal;a first main bonding wire (300 a) connected between the firstbonding pad and a third bonding pad (332); a second main bonding wire(300 b) connected between the second bonding pad and a fourth bondingpad (334); a sub bonding wire (305) connected between the third bondingpad (332) and the fourth bonding pad (334); said first main bonding wireincluding a first member (351) bonded to the first bonding pad, a secondmember (353) coupled to the first member and rising from the mainsurface of the substrate in a direction opposing to the third bondingpad; a third member (355) coupled to the second member and rising up toa wire loop height in a direction toward the third bonding pad, and afourth member (357) coupled to the third member and descending towardthe third bonding pad to be bonded to the third bonding pad; said secondmain bonding wire including a first member (351) bonded to the fourthbonding pad, a second member (353) coupled to the first member andrising from the main surface of the substrate in a direction opposing tothe second bonding pad; a third member (355) coupled to the secondmember and rising up to a wire loop height in a direction toward thesecond bonding pad, and a fourth member (357) coupled to the thirdmember and descending toward the second bonding pad to be bonded to thesecond bonding pad; said wire loop height of the first and second mainbonding wires ranged from 100 μm to 1,000 μm; and said sub bonding wireelectrically interconnecting the third and fourth boding pads in placeof a metal strip line (105).

A spiral inductor is shown in FIG. 4B as a comparative example to thebonding wire inductor according to the present invention. In thefabricated spiral inductor, an air bridge line for connecting the centerof a spiral arm and a port was fabricated to a height of 120 μm by thewire bonding process. By using the wire bonding process, additionalphotolithography and metallization processes for forming the air bridgeline could be omitted. The spiral inductor had the same line width, linespacing and number of turns as those of a high Q-inductor which isdesigned by Shih. The stripline of the fabricated spiral inductor had a0.82 μm-thickness, a 20 μm-line width and a 15 μm-line spacing. Thebonding height, length and shape, which are parameters determining theelectrical characteristics of the bonding wire inductor could beautomatically controlled due to a continuous development of bonder andbonding technology.

After the wire bonding process, the bonding wire inductor was fixed by aplastic molding or hermetic packaging process. In the plastic molding,the bonding wire is molded by FR-4 composite or epoxy resin (E010116j,manufactured by HYSOL, Japan) having a dielectric constant of 4.3, sothat mechanical and electrical characteristics thereof can be maintainedto be stable. More stable characteristics can be achieved by coating thebonding wire with an insulating material before the molding process. TheFR-4 component as a polymeric compound, is widely used as a lowfrequency plastic molding compound (EMC) and for a printed circuit board(PCB) due to its mechanical and electrical stability and economicalmerit. In the hermetic packing, as shown in FIG. 5, the bonding wires 1formed on the substrate 9 are sealed by ceramic, plastic or metal 17.Here, in order to prevent vibration of the bonding wires 1, the upperpart of the bonding wires 1 can be fixed by epoxy resin 19. In addition,in the vertical bonding wire inductor according to the presentinvention, a magnetic material (not shown) may be inserted into the loopformed by the bonding wires 1.

Also, the electrical characteristics such as inductance and Q-factor, ofthe bonding wire inductor according to the present invention varyaccording to the shape of the bonding wire (height or area of the loop).Thus, the shape of the formed bonding wires can be changed mechanicallybefore the packing process, so that bonding wire inductors havingvarious electrical characteristics can be manufactured with a highdegree of freedom in designing.

Embodiment 2

Test of Characteristics of Bonding Wire Inductors and Spiral Inductorson GaAs Substrate

The S-parameters of the bonding wire inductors and spiral inductorsmanufactured in Embodiment 1 were measured using a vector networkanalyzer (HP 8510C) and a cascade microwave probe station [David M.Pozar, 1990, Microwave Engineering, Addision-Wesley Publishing Co.,Inc., pp. 220-221]. For the measurement, LRM calibration was performedon Impedance Standard Substrate (ISS) and a de-embedding process wasperformed in order to remove the effects of test jig.

The inductance and Q-factor of the bonding wire inductor according tothe present invention, formed by connecting a pair of bonding padshaving a size of 90×90 μm, which were formed on a GaAs substrate, withonly one bonding wire, were measured by on-wafer measurement by varyingthe bonding length from 0.3 mm to 1.3 mm and the measurement frequencyfrom 1 GHz to 25 GHz. The results are shown in FIGS. 6 and 7. FIG. 6shows that the inductance is in the range of 1-1.8 nH at 1 GHz and theresonant frequency is in the range of 16-23 GHz. As can be seen fromFIG. 7, the bonding wire has the maximum Q-factor at the frequency of 6GHz and the Q-factor is in the range of 44-58 at the inductance range of1-1.8 nH. The reason for a slow decrease in the Q-factor at thefrequency of 6 GHz or more showing the maximum Q-factor is that theohmic loss of the bonding wire increases at this frequency.

The multi-loop bonding wire inductor and the spiral inductor formed on aGaAs substrate were measured by on-wafer measurement while varying thefrequency in the range of 1-10 GHz, and the S-parameters of a 2-portnetwork were plotted on the Smith chart of FIG. 8. Among theS-parameters, S12 is equivalent to S21 by the reciprocity theorem andS22 approximates S11 due to symmetrical structure, so that only S11 andS21 are represented in FIG. 8. The inductance and the Q-factor of thedevice were extracted by using input impedance obtained from theS-parameters measured when one port of the inductor was grounded, andthe results are shown in FIGS. 9 and 10. In FIGS. 9 and 10, SPIRALindicates the spiral inductor and BW indicates the bonding wireinductor. Also, reference numerals such as 3.5 and 4 represent thenumber of turns or the number of loops. These legends provide the samemeaning in other drawings.

FIG. 9 shows that the inductance of the bonding wire inductor increasesas the number of loops of the bonding wire inductor increases, similarto the increase in the number of turns of the spiral inductor.

The inductances of 3-loop bonding wire inductor consisting of threewires and 4-loop bonding wire inductor consisting of four wires, showthe same characteristics as those of 3.5-turn and 2.5-turn spiralinductor, respectively. Because the spiral inductor structurally has anarrow loop spacing, the mutual inductance is increased, resulting in adesired high inductance. However, the bonding wire inductor which has aloop spacing wider than that of the spiral inductor, can effectivelyproduce high inductance by enlarging bonding wire loops perpendicular tothe ground plane. FIGS. 9 and 10 show that the bonding wire inductor hasan improved resonant frequency compared to the spiral inductor havingsimilar inductance. The reason for this is that in view of the mutualcapacitance which is a critical factor in determining the resonantfrequency of the inductor, the bonding wire inductor shows a smallparasitic mutual capacitance characteristic due to the loop pitch ofmore than 85 μm. FIGS. 9 and 10 also show the inductances, resonantfrequencies and the Q-factors of the bonding wire inductor and spiralinductor, calculated by FEM analysis. The Q factors of the spiralinductors are less than 10 while the bonding wire inductors according tothe present invention have very high Q-factors of more than 23.

In order to investigate the reason for the improved high Q-factor of thebonding wire inductor, resistance characteristics of an unloadedinductor are shown in FIG. 11. As shown in FIG. 11, the resistance ofthe bonding wire inductor is relatively low with respect to the spiralinductor at the frequency lower than the usable frequency range.

For efficient comparison between the bonding wire inductor according tothe present invention and the spiral inductor, electricalcharacteristics thereof are shown in TABLE 1.

As can be seen in TABLE 1, the 3-loop bonding wire inductor has equalinductance to the 2.5-turn spiral inductor. However, the resonantfrequency and Q-factor of the bonding wire inductor are improved byabout 7% and 223%, respectively. Also, the 4-loop bonding wire inductorshows similar electrical characteristics to those of the 3.5-turn spiralinductor.

Embodiment 3

Fabrication of Vertical Bonding Wire Inductors on GaAs Substrate andTest of Characteristics Thereof

Vertical bonding wire inductors and spiral inductors were designed andfabricated in the same manner as in Embodiment 1, except that thethickness of the metal strip formed on the GaAs substrate was adjustedto 2 μm, rather than 0.82 μm. FIG. 12 comparatively shows theinductances of the fabricated vertical bonding wire inductor and spiralinductor. Referring to FIG. 12, the 3-loop and 4-loop vertical bondingwire inductors have similar inductances to the 2.5-turn and 3.5-turnspiral inductors, respectively. They also have higher resonantfrequencies than those of the spiral inductors. FIG. 13 is a graphcomparatively showing the Q-factors of the vertical bonding wireinductors and the spiral inductors. As shown in FIG. 13, the 2-loop,3-loop and 4-loop vertical bonding wire inductors have Q-factors higherthan those of the 2.5-turn, 3.5-turn and 4.5-turn spiral inductors.FIGS. 14 and 15 comparatively show the inductances and Q-factors of the3-loop and 4-loop vertical bonding wire inductors and the 3.5-turnspiral inductor, respectively, before and after molding. It can be seenthat the resonant frequency and the Q-factor are decreased after moldingin both the vertical bonding wire inductors and the spiral inductor.

TABLE 1 Comparison of measured electrical characteristics of thevertical bonding wire inductor and spiral inductor on GaAs substrateComparison 1 Comparison 2 Spiral Vertical Spiral Vertical Electricalinductor bonding wire inductor bonding wire characteristics (2.5 turns)(2 wire loops) (3.5 turns) (4 wire loops) Inductance at 3.5 3.5 5.1 5.31 GHz (nH) Resonant 8.6 9.2 7 7.2 frequency (GHz) Resistance at 6.9 2.29.2 3.1 1 GHz (Ω) Q-factor 8.2 26.5 7.7 23.2 (f_(Qmax) (GHz)) (3.2)(3.7) (3) (3)

Embodiment 4

Fabrication of Vertical Bonding Wire Inductors on Silicon Substrate andTest of Characteristics Thereof

Vertical bonding wire inductors and spiral inductors were designed andfabricated in the same manner as in Embodiment 3 except that a p-typesilicon substrate (15 Ω-cm) was used instead of the GaAs substrate usedin Embodiment 3. The thickness of the metal strip was 2 μm and thethickness of a SiO₂ insulation layer was 2 μm.

In general, Si substrates have higher conductivities than those of GaAssubstrates. In particular, Si substrates used in the semiconductor fieldare doped with impurities over the entire surface, so that theconductivity is further increased. In the case of using a Si substrate,a thin silicon oxide layer is formed on the substrate prior to theformation of a device, while a device is formed directly on a GaAssubstrate. Also, in the aspect of substrate and ohmic losses whichaffect the Q-factor, the substrate loss in the GaAs substrate isnegligible while the ohmic loss therein is considerable. In contrast,the substrate loss in a Si substrate is 3-5 times higher than theconductor loss. Prior to forming a device on a Si substrate,pre-considerations which are different from those for using GaAssubstrate, are required.

FIG. 16 is a graph showing the inductances of both the vertical bondingwire inductors and the spiral inductors. As shown in FIG. 16, theinductances of the 3-loop and 4-loop vertical bonding wire inductors aresimilar to the 2.5-turn and 3.5-turn spiral inductors, respectively.Also, the resonant frequencies of the vertical bonding wire inductorsare higher than those of the spiral inductors. FIG. 17 comparativelyshows the Q-factors of the vertical bonding wire inductors and thespiral inductors. It can be seen from FIG. 17 that the Q-factors of the2-loop, 3-loop and 4-loop vertical bonding wire inductors are higherthan those of the 2.5-turn, 3.5-turn and 4.5-turn spiral inductors,respectively. FIGS. 18 and 19 comparatively show the inductances andQ-factors of the 3-loop and 4-loop vertical bonding wire inductors andthe 2.5-turn and 3.5-turn spiral inductor, respectively, before andafter molding. It can be seen that the resonant frequencies andQ-factors of both the vertical bonding wire inductors and the spiralinductors are decreased after molding.

Also, compared with the inductance of the vertical bonding wire inductorformed on a GaAs in Embodiment 3 under similar conditions to thisembodiment, shown in FIG. 12, the inductance of the inductor on a Sisubstrate, manufactured in this embodiment, is not significantlydifferent from that of the inductor formed on the GaAs substrate inEmbodiment 3. Comparing the Q factors of the inductors manufactured inthis embodiment (FIG. 17) to those in Embodiment 3 (FIG. 13), theQ-factors of the inductors of this embodiment are smaller than those inEmbodiment 3. However, the Q-factors of the inductors formed on the Sisubstrate in this embodiment are much higher than those of conventionalspiral inductors. Summing up the results, the vertical bonding wireinductor according to the present invention can be formed in a Sisubstrate which is favorable to commercial use, providing bettercharacteristics than those of the conventional spiral inductors.

Embodiment 5

Fabrication of Vertical Bonding Wire Inductors on Silicon Substrate andTest of Characteristics Thereof

Vertical bonding wire inductors and spiral inductors were designed andfabricated in the same manner as in Embodiment 4 except that a p-typesilicon substrate (30 Ω-cm) was used instead of the p-type siliconsubstrate (15 Ω-cm) used in Embodiment 4. The thickness of the metalstrip was 2 μm and the thickness of a SiO₂ insulation layer was 2 μm.FIG. 20 is a graph showing the inductances of both the vertical bondingwire inductors and the spiral inductors. As shown in FIG. 20, theinductances and resonant frequencies of the 3-loop and Sloop verticalbonding wire inductors are similar to the 2.5-turn and 3.5-turn spiralinductors, respectively. FIG. 21 comparatively shows the Q-factors ofthe vertical bonding wire inductors and the spiral inductors. It can beseen from FIG. 21 that the Q-factors of the 2-loop, 3-loop and 4-loopvertical bonding wire inductors are higher than those of the 2.5-turn,3.5-turn and 4.5-turn spiral inductors, respectively. FIGS. 22 and 23comparatively show the inductances and Q-factors of the 3-loop and4-loop vertical bonding wire inductors and the 2.5-turn and 3.5-turnspiral inductor, respectively, before and after molding. It can be seenthat the resonant frequencies and Q-factors of both the vertical bondingwire inductors and the spiral inductors are decreased after molding.

For effective comparison between the vertical bonding wire inductors andthe spiral inductors, detailed electrical characteristics are tabulatedin TABLE 2.

TABLE 2 Comparison of electrical characteristics between verticalbonding wire inductors and spiral inductors on p-type silicon substrate(30 Ω-cm) Vertical bonding wire inductor (Si—P type 30 Ω-cm) Electrical105 μm-pad 100 μm-pad 85 μm-pad Spiral characteristics pitch pitch pitchinductor Inductance at 500 MHz (nH) 2 loops 2 2 2.1 — 3 loops 3.2 3.33.5 3.5 (2.5 turns) 4 loops 4.7 4.8 5 5 (3.5 turns) Q_(max) 2 loops 3032 34 — (3 GHz) (3 GHz) (3 GHz) 3 loops 18 20 22 8 (1.8 GHz) (1.8 GHz)(1.8 GHz) (1.5 GHz) (2.5 turns) 4 loops 14 15 16 7 (1 GHz) (1 GHz) (1GHz) (1.2 GHz) (3.5 turns) Q-factor at 3 GHz 2 loops 30 32 34 — 3 loops14 16 18 5.5 (2.5 turns) 4 loops 7 9 10 4.5 (3.5 turns) Resonantfrequency (GHz) 2 loops >15 >15 >15 — 3 loops 13 13.5 14 11 (2.5 turns)4 loops 9.5 10 11 9.5 (3.5 turns)

From TABLE 2, it can be seen that the Q-factors and the resonantfrequencies of the vertical bonding wire inductors according to thepresent invention are much higher than those of the spiral inductors.Also, the inductances of the 3-loop and 4-loop bonding wire inductorsare nearly equal to those of the 2.5-turn and 3.5-turn spiral inductors,respectively.

Embodiment 6

Fabrication of Vertical Bonding Wire Inductor Having Bonding PadsConnected by Only Bonding Wires and Test of Characteristics Thereof

Vertical bonding wire inductors were fabricated in the same manner as inthe preceding embodiments, except that the bonding pads were diagonallyconnected by stitch bonding wires instead of metal strips. By usingautomatic stitch bonding machine having a rotary head, the bonding padson the GaAs or silicon substrate were diagonally connected, resulting inthe stitch bonding wires which have a low bonding height (about 100 μm)compared to the case of using the metal strips. As a result, as shown inFIGS. 24A and 24B, another vertical bonding wire inductor according tothe present invention, which comprises only bonding wires, having atrapezoidal loop shape, was formed. The resistance of the verticalbonding wire inductor including only the bonding wires is lower thanthose of the vertical bonding wire inductors manufactured in thepreceding embodiments, so that the Q-factor thereof is greatlyincreased. Also, the parasitic capacitance of the vertical bonding wireinductor of this embodiment is lower than that of the vertical bondingwire inductor having the metal strips, thereby significantly increasingthe resonance frequency. Also, the process for forming metal strips,performed in the preceding embodiments, is not performed, so that themanufacturing process can be further simplified.

The resistance of the vertical bonding wire inductor of this embodimentwas calculated from measured resistance of a single bonding wire byusing the Phenomenological loss equivalence method [H. Y. Lee and T.Itho, 1989, Phenomenological loss equivalence method for planarquassi-TEM transmission lines with a thin normal conductor orsuperconductor, IEEE Trans. Microwave Theory and Tech., Vol. MTT-37, No.12, pp. 1904-1909]. As a result, the loop area was reduced by the stitchbonding, so that the inductance of the inductor was decreased by about10% and the parasitic capacitance was decreased by about 34%. FIG. 25Ashows the Q-factors of the vertical bonding wire inductors with respectto the frequency. As shown in FIG. 25A, the Q-factors are greatlyimproved at low frequencies. At a frequency lower than 5 GHz, theQ-factor of the Sloop bonding wire inductor was higher than those of the2-loop and 3-loop bonding wire inductors, because an increase in themagnetic flux linkage is more prominent than that in the resistance foran increase in the number of loops. As described above, because theparasitic capacitance due to the metal strips is not produced, adecrease in the Q-factor due to resonance does not occur at frequencieslower than 5 GHz. The maximum Q-factor and usable frequency range of thevertical bonding wire inductors of this embodiment are similar to thoseof the off-chip inductor. In addition, because the parasitic factors arenot present, which are caused by external interconnection lines in theoff-chip inductor, the vertical bonding wire inductor of this embodimentshows significantly more efficient characteristics.

Embodiment 7

Fabrication of Vertical Bonding Wire Inductor Having Bonding PadsConnected by Only Bonding Wires and Test of Characteristics Thereof

The bonding wire inductor shown in FIG. 24C was fabricated as anotherembodiment of the present invention. This bonding wire inductor the sameas the bonding wire inductor shown in FIG. 24B, fabricated in Embodiment6, in that all connection between bonding pads was achieved by bondingwires. However, in the bonding with inductor of FIG. 24C, a siliconsubstrate (15 Ω-cm) having a 2 μm-thick SiO₂ insulating layer was usedand the connection of facing bonding pads in a parallel direction wasachieved with bonding wires by stitch bonding, while the connection ofthe bonding pads in a diagonal direction was achieved with bonding wiresby ball bonding, which is the difference from the bonding wire inductorof FIG. 24B. Each inductor loop included two bonding pads and upper andlower bonding wires. The upper and lower bonding wires were made of gold(Au) having a diameter of 33 μm. Also, the average heights of upperloops formed by the upper bonding wires, and the lower loops formed bythe lower bonding wires, were 500 μm and 50 μm, respectively and theloop pitch was 85 μm. The bonding wires connect the bonding pads each of80×80 μm, and occupy the area of 400×770 μm. The thickness of thesilicon substrate was 500 μm and a 2 μm-thick SiO₂ insulating layer wasformed thereon. The metal pattern was formed by deposition of Au(0.8μm)/Cr(200 Å) and by the lift-off process. As a result, another verticalbonding wire inductor having a trapezoidal loop shape was formed, asshown in FIG. 24C. The S-parameters of the inductor were measured by avector network analyzer and a microwave probe station in the frequencyrange of 0.5-20 GHz. The parasitic capacitance of a probe pad waseffectively de-embedded using the S-parameters according to the opencoplanar waveguide standard.

FIG. 25B comparatively shows the inductances of the vertical bondingwire inductors of this embodiment and the spiral inductors. As shown inFIG. 25B, as the number of loops increases, the inductances of thebonding wire inductors increase while the resonant frequencies decrease.The result can also be obtained with an increase in the number of turnsof the spiral inductor. The inductance of the 3-loop bonding wireinductor is nearly equal to that of the 3-turn spiral inductor, and theresonant frequency thereof is slightly higher than that of the 3-turnspiral inductor.

FIG. 25C shows the Q-factors of the vertical bonding wire inductors ofthis embodiment and the spiral inductors. As shown in FIG. 25C, theQ-factors of the bonding wire conductors are much higher than those ofthe spiral inductors. This is due to a low ohmic loss of the verticalbonding wire inductors and a low substrate loss by arranging the bondingwire inductor perpendicular to the silicon substrate.

For effective comparison between the vertical bonding wire inductors andthe spiral inductors on the silicon substrate (15 Ω-cm), the electricalcharacteristics thereof are tabulated in TABLE 3.

The resonant frequency and the Q-factor of the 3-loop bonding wireinductor of this embodiment are increased by about 3 GHz and 300%,respectively.

Embodiment 8

Fabrication of Vertical Bonding Wire Inductor Having Bonding PadsConnected by Only Bonding Wires and Test of Characteristics Thereof

The bonding wire inductor shown in FIG. 24D was fabricated as yetanother embodiment of the present invention. This bonding wire inductoris the same as the bonding wire inductor shown in FIGS. 24B and 24C,fabricated in Embodiments 6 and 7, in that all connection betweenbonding pads was achieved by bonding wires. However, unlike the bondingwire inductors of FIGS. 24B and 24C, the connection of the bonding padsin both parallel and diagonal directions was achieved by ball bonding.As a result, another vertical bonding wire inductor having a trapezoidalloop shape was obtained, as shown in FIG. 24D. The electricalcharacteristics of the bonding wire inductors according to the presentinvention, such as inductance and Q-factor, were similar to those inEmbodiment 7.

TABLE 3 Comparison of electrical characteristics between verticalbonding wire inductors and spiral inductors on silicon substrate (15Ω-cm) 2 turns or loops 3 turns or loops 4 turns or loops ElectricalBonding Bonding Bonding characteristics Spiral wire Spiral wire Spiralwire Inductance 3.4 2.8 5 4.9 6.2 7.4 at 1 GHz (nH) Resonant 11.2 19.6 912 8.2 11.6 frequency (GHz) Q-factor 7 29 6 18 5 9.9 (f_(Qmax) (GHz))(1.8) (2) (1.2) (0.8) (1.1) (0.5)

The bonding wire inductor according to the present invention can be usedin couplers, transformers or other radio frequency devices, wherein twobonding wire inductors are arranged in each device. That is, as shown inFIG. 26, one bonding wire inductor including bonding wires 1 a, bondingpads 3 a, metal strips 5 a and input/output ports 7 a, and the otherbonding wire inductor including bonding wires 1 b, bonding pads 3 b,metal strips 5 b and input/output ports 7 b, may be arranged such thatthey overlap each other, for use in a coupler or transformer. In such acase, where two or more bonding wire inductors are arranged such thatthey are adjacent to each other, it is more effective to arrange thebonding wire inductors such that the direction of the magnetic fieldsthereof are perpendicular to each other as shown in FIG. 27, therebyminimizing magnetic interference. Also, in the bonding wire inductors ofFIGS. 26 and 27, the metal strips were used for the connection betweenthe bonding pads in a diagonal direction. However, the metal strips canbe replaced by stitch bonding wires or ball bonding wires as shown inFIGS. 24A through 24D.

As described above, according to the results of simulation in which theelectrical characteristics of the bonding wire inductor were analyzed byvarying the frequency range to 10 GHz, the inductance of the bondingwire inductor was improved by about 6%, and the resonant frequency andthe Q-factor thereof were also improved by about 8.5% and 360%,respectively, compared to the spiral inductor having the same area underthe same environment. Also, the resonant frequency and Q-factor of thevertical bonding wire inductors according to the present invention,formed on the GaAs substrate and silicon substrate, were improvedcompared to the spiral inductors. In particular, the Q-factor and theresonant frequency of the vertical bonding wire inductors includingbonding pads connected by only bonding wires are much higher than thoseof the vertical bonding wire inductor in which a metal strip is used forthe connection. Thus, such bonding wire inductors, which use onlybonding wires for the connection are more effective for practical use.

INDUSTRIAL APPLICABILITY

Also, the method for manufacturing an inductor for RFICs or MMICsaccording to the present invention does not require an air bridgeprocess for the connection at the center of the inductor as does aconventional method for manufacturing a spiral inductor, which has aproblem, thus additional photolithography and metallization processesare not required, thereby simplifying the overall process in addition toreducing the manufacturing cost. Due to the improved electricalcharacteristics, stability in process, tunability without additionalmask manufacturing processes, and relatively low manufacturing cost, thevertical bonding wire inductor according to the present invention can beuseful in production of economical microwave devices.

What is claimed is:
 1. A bonding wire inductor comprising: a firstinductor terminal and a second inductor terminal formed on a substratehaving a main surface; a first bonding pad connected to the firstinductor terminal; a second bonding pad connected to the second inductorterminal; a first bonding wire connected between the first and secondbonding pads; said first bonding wire including a first member bonded tothe first bonding pad, a second member coupled to the first member andrising from the main surface of the substrate in a direction opposing tothe second bonding pad; a third member coupled to the second member andrising up to a wire loop height in a direction toward the second bondingpad, and a fourth member coupled to the third member and descendingtoward the second bonding pad to be bonded to the second bonding pad;and said wire loop height ranging from 100 μm to 1,000 μm.
 2. Thebonding wire inductor of claim 1, wherein the bonding wire inductor isfixed by magnetic material inserted into the bonding wires.
 3. Thebonding wire inductor of claim 1, further comprising a third bonding padand a fourth bonding pad connected between the second inductor terminaland the second bonding pad, and at least one second bonding wireconnected between the third and fourth bonding pads, and wherein: saidsecond bonding wire includes a first member bonded to the third bondingpad, a second member coupled to the first member and rising from themain surface of the substrate in a direction opposing to the fourthbonding pad; a third member coupled to the second member and rising upto a wire loop height in a direction toward the fourth bonding pad, anda fourth member coupled to the third member and descending toward thefourth bonding pad to be bonded to the fourth bonding pad; said wireloop height ranging from 100 μm to 1,000 μm; and said second and thirdboding pads are electrically interconnected by a metal strip line. 4.The bonding wire inductor of claim 3, wherein the second bonding wire isball bonded to one of the third and fourth bonding pads and is wedgebonded to the other one of the third and fourth bonding pads.
 5. Thebonding wire inductor of claim 1, wherein the first bonding wire is ballbonded to one of the first and second bonding pads and is wedge bondedto the other one of the first and second bonding pads.
 6. The bondingwire inductor of claim 1, wherein the substrate is a gallium arsenide(GaAs) substrate, a silicon substrate, an alumina substrate, afluorineresin substrate, an epoxy substrate, a ceramic substrate, asilicon-on-insulator (SOI) substrate, a lithium tantalite (LiTaO₃)substrate, a lithium niobate (LiNbO₃) substrate, a low temperatureco-fired ceramic (LTCC) substrate, a quartz substrate, a glass substrateor a printed circuit board.
 7. A chip inductor formed by individuallypackaging the bonding wire inductor of claim
 1. 8. A coupler formed byarranging two bonding wire inductors of claim 1 adjacent to one another.9. A transformer formed by arranging two bonding wire inductors of claim1 adjacent to one another.
 10. A bonding wire inductor comprising: afirst inductor terminal and a second inductor terminal formed on asubstrate having a main surface; a first bonding pad connected to thefirst inductor terminal; a second bonding pad connected to the secondinductor terminal; a first main bonding wire connected between the firstbonding pad and a third bonding pad; a second main bonding wireconnected between the second bonding pad and a fourth bonding pad; a subbonding wire connected between the third bonding pad and the fourthbonding pad; said first main bonding wire including a first memberbonded to the first bonding pad, a second member coupled to the firstmember and rising from the main surface of the substrate in a directionopposing to the third bonding pad; a third member coupled to the secondmember and rising up to a wire loop height in a direction toward thethird bonding pad, and a fourth member coupled to the third member anddescending toward the third bonding pad to be bonded to the thirdbonding pad; said second main bonding wire including a first memberbonded to the fourth bonding pad, a second member coupled to the firstmember and rising from the main surface of the substrate in a directionopposing to the second bonding pad; a third member coupled to the secondmember and rising up to a wire loop height in a direction toward thesecond bonding pad, and a fourth member coupled to the third member anddescending toward the second bonding pad to be bonded to the secondbonding pad; said wire loop height of the first and second main bondingwires ranged from 100 μ to 1,000 μm; and said sub bonding wireelectrically interconnecting the third and fourth boding pads in placeof a metal strip line.
 11. The bonding wire inductor of claim 10,wherein the sub bonding wire is wedge bonded to both the third andfourth bonding pads.
 12. The bonding wire inductor of claim 10, whereinthe sub bonding wire is ball bonded to one of the third and fourthbonding pads and is wedge bonded to the other one of the third andfourth bonding pads.
 13. The bonding wire inductor of claim 10, whereinthe bonding wire inductor is fixed by magnetic material inserted intothe bonding wires.
 14. The bonding wire inductor of claim 10, whereinthe substrate is a gallium arsenide (GaAs) substrate, a siliconsubstrate, an alumina substrate, a fluorineresin substrate, an epoxysubstrate, a ceramic substrate, a silicon-on-insulator (SOI) substrate,a lithium tantalite (LiTaO₃) substrate, a lithium niobate (LiNbO₃)substrate, a low temperature co-fired ceramic (LTCC) substrate, a quartzsubstrate, a glass substrate or a printed circuit board.
 15. A chipinductor formed by individually packaging the bonding wire inductor ofclaim
 10. 16. A coupler formed by arranging two bonding wire inductorsof claim 10 adjacent to one another.
 17. A transformer formed byarranging two bonding wire inductors of claim 10 adjacent to oneanother.